1. Field of the Invention
The present invention relates to a packaging bag in which a main bag body can be kept in a prescribed shape by means of a framework member, and to a method for manufacturing such a packaging bag.
2. Description of the Related Art
There have conventionally been various kinds of packaging bags made of plastic film material. There has recently been a strong demand to cause such a packaging bag to receive products such as teabags having predetermined shapes, without collapsing their shapes. The applicant has pursued the development of a packaging bag in response to the above-mentioned demand. Such a packaging bag is composed of a main bag body made of plastic film material and a sleeve disposed therein. The sleeve is foldable/unfoldable and is inserted into the main bag body from an opening thereof. Accordingly, the sleeve received in the main bag body is foldable/unfoldable together with the main bag body, to enable the sleeve and the main bag body to be shifted between a generally flat collapsed state and an expanded state. Japanese Laid-Open Patent Application No. 2001-322187 discloses such a packaging bag and technical effects provided by it.
In the above-mentioned packaging bag, it is essential to place the sleeve having a suitable size to the main bag body in proper position in the main bag body, in order to provide an excellent external appearance of the packaging bag in the expanded state.
However, it is not easy to insert the sleeve having the suitable size into the main bag body from the opening thereof. More specifically, when the length of the opening of the main bag body, which is kept in the collapsed state, is identical to the width of the sleeve, which is also kept in the collapsed state, the total thickness of the collapsed sleeve makes it difficult to insert the sleeve into the main bag body, because of no existence of gusset. In case where the main bag body is provided in its opening with a linear fastener, the liner fastener makes the insertion operation of the sleeve more difficult. Such difficulty in insertion operation of the sleeve deteriorates a manufacturing efficiency of the packaging bag, thus leading to an increased manufacturing cost thereof.
It is conceivable to reduce the size of the sleeve in order to facilitate the inserting operation of the sleeve into the main bag body. In this case, the sleeve kept in the expanded state is loosely fitted into the main body kept in the same expanded state to cause a large gap between the sleeve and the main body, thus deteriorating an external appearance of the packaging bag.